Avalanche Forecast

Issued: Mar 13th, 2014 9:48AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Storm Slabs, Loose Wet and Deep Persistent Slabs.

bcorrigan, Avalanche Canada

Kootenay Boundary.

The hazard may go up in the afternoon with daytime warming. For more insight into the current tricky snowpack, check out the most recent:Forecasters Blog.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: The ridge of high pressure begins to break down with incoming Pacific frontal systems.Tonight: Clear periods, no precipitation in the forecast, freezing level around 600 metres, ridge top winds light from the south west, occasionally gusting to strong.Friday: Cloudy, 5 to 10cm of precipitation, freezing level around 1400 metres, winds from the southwest , light to moderate, occasionally gusting to strong.Saturday: Cloudy with a trace of precipitation, freezing level around 1500 metres, ridge top winds moderate to strong from the south west.Sunday: Cloudy, light to locally moderate precipitation, ( 5 to 15cm) freezing level may climb to 1600 metres.

Avalanche Summary

We've received reports of large ( size 2 and 3 ) natural avalanches in the region. Cornice failures and resulting large avalanches are being reported in the Kootenay-Boundary region and in the neighboring areas as well. Careful attention to daytime warming and aspect will be necessary to ride safely in the back country.

Snowpack Summary

Warm temperatures have promoted rapid settlement of the recent storm snow into a dense slab that sits above a variety of old surfaces. Overnight freezing will help seal up the surface from the weak layers buried below, at least until warm daytime temperatures break down the surface crust, then all bets are off ! Rain up to 1900m has saturated the upper snowpack in some parts of the forecast area and will crust-over as the freezing level lowers at night. At elevations above the freezing level strong SW winds have have formed significant winds slabs in lee features adding load to the storm slab overlying a variety of persistent weak layers.3 persistent weak layers are buried in the snowpack, A January 28th layer of surface hoar, facets and crusts, a Feb.10th layer of surface hoar, facets and crusts now almost 200cm down,... and the March 2nd layer of surface hoar, facets and crusts at approximately 120cm from the surface.. Of these layers, the Feb. 10th/Jan. 28th layers still appear to be problematic with field reports indicating easy and sudden planar shears on this layer, especially on north aspects. Some parts of the forecast region recently received 5cm of new snow.

Problems

Storm Slabs

Daytime heating and solar input are critical now. Storm snow on solar aspects may be on a sun crust that is touchy and quite reactive. South west winds have formed wind slabs on lee slopes at tree line and above. Cornices may present a real hazard.

Be alert to conditions that change with elevation.>Choose conservative lines and watch for clues of instability.>Make observations and assess conditions continually as you travel.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

2 - 4

Loose Wet

Incoming storms will most likely be rain below 1800 metres, further saturating and already wet snowpack below treeline.

The new snow will require several days to settle and stabilize.>Watch for terrain traps where small amounts of snow will acumulate into deep deposits.>Avoid steep, open glades in the forest.>Assess start zones carefully and use safe travel techniques.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Deep Persistent Slabs

Avoid unsupported slopes.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 14th, 2014 2:00PM